Group A rotavirus infections are the most common cause of severe gastroenteritis among infants and young children worldwide. The rhesus rotavirus (RRV)-based quadrivalent vaccine developed in this laboratory was licensed by FDA in 1998. A second generation vaccine, the bovine rotavirus UK-based quadrivalent vaccine has been undergoing phase I-II human trials. Rotavirus surface proteins VP4 and VP7 have been shown to be independent protective antigens. Recently, in studies by others in a mouse model, (i) certain IgA monoclonal antibodies directed to the rotavirus inner capsid protein VP6 were reported to be protective against disease, and (ii) antibodies directed to the rotavirus nonstructural protein NSP4 (viral enterotoxin) were shown to be effective passively in protection against disease. More recently, an immunocytochemistry assay was developed, in which Sf-9 cells infected with recombinant baculovirus that expresses a specific rotavirus protein as an antigen was utilized to assess immune response. In order to establish an immunocytochemistry assay in our laboratory for an assessment of immune response to selected rotavirus proteins following natural rotavirus infection or vaccination, we constructed recombinant baculoviruses expressing rotavirus (i) outer capsid protein VP7 of human rotavirus (HRV) D (G1), DS-1 (G2), P (G3), ST3 (G4) and AU32 (G9), (ii) outer capsid VP4 of RRV (P5B) and bovine UK (P7), and (ii) nonstructural protein NSP4 of HRV Wa (genotype B), DS-1 (genotype A), RRV (genotype C) and porcine SB-1A (genotype B).